This invention relates to a rack and pinion steering gear for a motor vehicle.
A typical rack and pinion steering gear for a motor vehicle includes a housing, a rack bar having a rack gear thereon, a pinion gear rotatably supported on the housing, and a rack bearing which slidably engages the rack bar and resiliently thrusts the rack gear against the pinion gear. The pinion gear and the rack bearing constitute a first bearing supporting the rack bar on the steering gear housing for back and forth linear translation in the direction of a longitudinal centerline of the rack bar concurrent with rotation of the pinion shaft. A bushing on the steering gear housing remote from the pinion gear and the rack bearing constitutes a second bearing supporting the rack bar on the steering gear housing for back and forth linear translation in the direction of the longitudinal centerline of the rack bar. Opposite ends of the rack bar are linked by tie rods to respective ones of a pair of steering knuckles supported on a body of the motor vehicle for vertical suspension excursions and for rotation about vertical steering axes of the motor vehicle. Each steering knuckle has a dirigible road wheel rotatably supported thereon. Back and forth linear translation of the rack bar in the direction of its longitudinal centerline pivots the steering knuckles about the steering axes to steer the motor vehicle.
When the motor vehicle is in motion, the tie rods transfer forces from the steering knuckles to the ends of the rack bar which can cause the rack bar to vibrate. A variable which affects the frequency and amplitude of such vibrations and which is usually beyond the control of the manufacturer of the steering gear is the xe2x80x9coverhang distancexe2x80x9d of the rack bar, i.e. the distance by which one end of the rack bar overhangs the bushing and other end of the rack bar overhangs the pinion gear and rack bearing. Typically, as the overhang distance increases, the intensity of the vibrations of the rack bar increases and the vibrations are more likely to induce momentary separation between the pinion gear and the rack gear which manifests itself as audible xe2x80x9crack bar rattlexe2x80x9d. A rack and pinion steering gear according to this invention includes structural elements for suppressing such rack bar rattle.
This invention is a new and improved rack and pinion steering gear including a housing, a rack bar having a rack gear thereon, a pinion gear rotatably supported on the housing, and a rack bearing which slidably engages the rack bar and resiliently thrusts the rack gear against the pinion gear. The pinion gear and the rack bearing constitute a first bearing supporting the rack bar on the steering gear housing for back and forth linear translation in the direction of a longitudinal centerline of the rack bar concurrent with rotation of the pinion shaft. A bushing on the steering gear housing remote from the pinion gear and the rack bearing constitutes a second bearing supporting the rack bar on the steering gear housing for back and forth linear translation in the direction of the longitudinal centerline of the rack bar. An outboard bearing on the steering gear housing on the opposite side of the pinion gear from the bushing thrusts the rack bar parallel to the direction of the rack bearing and includes an elastomeric ring seated in a seat on the steering gear housing symmetric with respect to the longitudinal centerline of the rack bar and a sleeve mounted eccentrically on the elastomeric ring and slidably engaging the rack bar. The outboard bearing suppresses separation between the pinion gear and the rack gear by supplementing the thrust of the rack bearing and by reducing the overhang distance of the rack bar.